package DemolinkedList;

public class MySingleLinkedList {
    public class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;
    //头插法
    public void addFirst(int data){
        ListNode cur = new ListNode(data);
        if(head == null) {
            head = cur;
            last = cur;//注意
            return;//注意
        }
        cur.next = head;
        head.prev = cur;
        head = cur;
    }
    //尾插法
    public void addLast(int data){
        ListNode cur = new ListNode(data);
        if(head == null) {
            head = cur;
            last = cur;//注意
            return;//注意
        }
        last.next = cur;
        cur.prev = last;
        last = cur;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index < 0  || index > size()) {
            return;
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == size()) {
            addLast(data);
            return;
        }
        ListNode cur = searchIndex(index);
        ListNode tmp = new ListNode(data);
        tmp.next = cur;
        cur.prev.next = tmp;
        tmp.prev = cur.prev;
        cur.prev = tmp;
    }
    //返回该下标节点
    public ListNode searchIndex(int index) {
        ListNode cur = head;
        int count = 0;
        while(count != index) {
            cur = cur.next;
            count++;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        if(head == null) {
            return false;
        }
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        if(head == null) {
            return;
        }
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    head = cur.next;
                    if(head != null) {
                        head.prev = null;
                    }else {
                        last = null;
                    }
                    return;
                }
                if(cur.next == null) {
                    cur.prev.next = cur.next;
                    last = cur.prev;
                    return;
                }
                cur.prev.next = cur.next;
                cur.next.prev = cur.prev;
                return;
            }
            cur = cur.next;
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        if(head == null) {
            return;
        }
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    head = cur.next;
                    if(head != null) {
                        head.prev = null;
                    }else {
                        last = null;
                    }
                    return;
                }
                if(cur.next == null) {
                    cur.prev.next = cur.next;
                    last = cur.prev;
                    return;
                }
                cur.prev.next = cur.next;
                cur.next.prev = cur.prev;
            }
            cur = cur.next;
        }
    }


    //得到单链表的长度
    public int size(){
        if(head == null) {
            return -1;
        }
        int count = 0;
        ListNode tmp = head;
        while(tmp != null) {
            count++;
            tmp = tmp.next;
        }
        return count;
    }
    //打印链表
    public void display(){
        if(head == null) {
            System.out.println("空指针");
        }
        ListNode tmp = head;
        while(tmp != null) {
            System.out.print(tmp.val + " ");
            tmp = tmp.next;
        }
        System.out.println();
    }
    public void clear(){
        ListNode cur = head;
        while(cur != null) {
            ListNode curN = cur.next;
            cur.next = null;
            cur.prev = null;
            cur = curN;
        }
        head = null;
        last = null;
    }
}
